1. Field of the Invention
The present invention relates to a fan motor.
2. Description of the Related Art
Axial fan motors arranged to produce axial air flows by rotating impellers using driving forces of motors have been known. The axial fan motors are, for example, installed in household electrical appliances, office automation appliances, transportation equipment, and so on, and are used for the purposes of cooling electronic components, circulating gases in device cases, and so on. In addition, such fan motors are sometimes used for circulating gases in server rooms in which a large number of electronic devices are installed. A known fan motor is described in, for example, JP-A 2007-218150.
The fan motor described in JP-A 2007-218150 includes a casing defining a wind channel inside thereof, and a rotor fan and a stator housed in the casing. Once this fan motor is driven, a plurality of blades of the rotor fan are caused to rotate to produce an axial air flow in the wind channel.
In recent years, there has been an increasing demand for an increase in efficiency of fan motors. However, if the flow rate of a fan motor is increased in order to improve the efficiency of the fan motor, noise inevitably increases. Accordingly, in recent years, there has been an increasing need for reducing noise of the fan motors. Meanwhile, in recent years, there has been an increasing demand for reducing the size of the fan motors. Therefore, it is not desirable to increase the size of a fan motor in order to achieve reduced noise. Accordingly, there has been a demand for a technique for reducing noise of a fan motor without increasing the size of a space in which the fan motor is installed.
A space in which the known fan motor described in JP-A 2007-218150 is installed is a space which includes flanges and is substantially square when viewed in an axial direction. In this case, spaces extending in the axial direction between the two flanges are dead spaces. That is, this fan motor has dead spaces covering only a part of the circumferential extent thereof. If a reduction in the noise of the fan motor can be achieved by utilizing such dead spaces, the reduction in the noise of the fan motor can be achieved without an increase in the size of the space in which the fan motor is installed.